1. Field of the Invention
This invention relates to 1,3-dihydroxy-20,20-dialkyl-vitamin D3 analogs, compositions comprising the analogs and methods of treatment of osteoporosis, secondary hyperparathyroidism, cancer and autoimmune diseases using such analogs.
2. Description of Related Art
a. Osteoporosis
Osteoporosis is the most common form of metabolic bone disease and may be considered the symptomatic, fracture stage of bone loss (osteopenia). Although osteoporosis may occur secondary to a number of underlying diseases, 90% of all cases appear to be idiopathic. Postmenopausal women are at risk for idiopathic osteoporosis (postmenopausal or Type I osteoporosis); another particularly high risk group for idiopathic osteoporosis is the elderly of either sex (senile or Type II osteoporosis). Osteoporosis has also been related to corticosteroid use, immobilization or extended bed rest, alcoholism, diabetes, gonadotoxic chemotherapy, hyperprolactinemia, anorexia nervosa, primary and secondary amenorrhea, transplant immunosuppression, and oophorectomy. Postmenopausal osteoporosis is characterized by fractures of the spine, while femoral neck fractures are the dominant features of senile osteoporosis.
The mechanism by which bone is lost in osteoporotics is believed to involve an imbalance in the process by which the skeleton renews itself. This process has been termed bone remodeling. It occurs in a series of discrete pockets of activity. These pockets appear spontaneously within the bone matrix on a given bone surface as a site of bone resorption. Osteoclasts (bone dissolving or resorbing cells) are responsible for the resorption of a portion of bone of generally constant dimension. This resorption process is followed by the appearance of osteoblasts (bone forming cells) which then refill with new bone the cavity left by the osteoclasts.
In a healthy adult subject, osteoblasts and osteoclasts function so that bone formation and bone resorption are in balance. However, in osteoporotics an imbalance in the bone remodeling process develops which results in bone being replaced at a slower rate than it is being lost. Although this imbalance occurs to some extent in most individuals as they age, it is much more severe and occurs at a younger age in postmenopausal osteoporotics, following oophorectomy, or in iatrogenic situations such as those resulting from corticosteroid therapy or the immunosuppression practiced in organ transplantation.
Various approaches have been suggested for increasing bone mass in humans afflicted with osteoporosis, including administration of androgens, fluoride salts, and parathyroid hormone and modified versions of parathyroid hormone. It has also been suggested that bisphosphonates, calcitonin, calcium, 1,25-dihydroxy vitamin D3 and some of its analogs, and/or estrogens, alone or in combination, may be useful for preserving existing bone mass.
Vitamin D3 is a critical element in the metabolism of calcium, promoting intestinal absorption of calcium and phosphorus, maintaining adequate serum levels of calcium and phosphorus, and stimulating flux of calcium into and out of bone. The D vitamins are hydroxylated in vivo, with the resulting 1xcex1,25-dihydroxy metabolite being the active material. Animal studies with 1,25-(OH)2 vitamin D3 have suggested bone anabolic activity. Aerssens et al., in Calcif Tissue Int, 55:443-450 (1994), reported upon the effect of 1xcex1-hydroxy vitamin D3 on bone strength and composition in growing rats with and without corticosteroid treatment. However, human usage is restricted to antiresorption due to the poor therapeutic ratio (hypercalciuria and hypercalcemia as well as nephrotoxicity).
Dechant and Goa, in xe2x80x9cCalcitriol. A review of its use in the treatment of postmenopausal osteoporosis and its potential in corticosteroid-induced osteoporosisxe2x80x9d, Drugs Aging [NEW ZEALAND 5 (4): 300-17 (1994)], reported that 1,25-dihydroxy vitamin D3 (calcitriol) has shown efficacy in the treatment of postmenopausal osteoporosis (and promise in corticosteroid-induced osteoporosis) based upon a clinical trial in 622 women with postmenopausal osteoporosis. Patients with mild to moderate disease (but not those with more severe disease) who received calcitriol (0.25 microgram twice daily) had a significant 3-fold lower rate of new vertebral fractures after 3 years of treatment compared with patients receiving elemental calcium 1000 mg/day. In patients commencing long term treatment with prednisone or prednisolone, calcitriol 0.5 to 1.0 micrograms/day plus calcium 1000 mg/day, administered with or without intranasal calcitonin 400 IU/day, prevented steroid-induced bone loss. Overall, calcitriol was well tolerated. At recommended dosages hypercalcaemia was infrequent and mild, generally responding to reductions in calcium intake and/or calcitriol dosage. The narrow therapeutic window of calcitriol required that its use be adequately supervised, with periodic monitoring of serum calcium and creatinine levels. This study clearly identifies the key limitation of calcitriol therapy as the close proximity of therapeutic and toxic doses.
This invention provides novel vitamin D3 derivatives which have more favorable therapeutic doses.
b. Cancer
Epidemiologic studies have correlated sun or UV light exposure with a lower incidence of a variety of malignancies, including breast, colon and prostate cancer. Evidence from receptor studies demonstrates that besides the classic target organs, such as intestine, kidney and bone, vitamin D receptors (VDR) are present on a wide variety of human normal and cancer cell lines and fresh tissue. Growth inhibition with vitamin D or 1,25-dihydroxycholecalciferol does not always translate into potential therapeutic efficacy in vivo. Early in vivo studies have focused on the anti-proliferative effects of 1,25-dihydroxycholecalciferol and its analogues in murine leukemia model systems where 1,25-dihydroxycholecalciferol has been shown to induce not only an anti-proliferative effect, but also a differentiating effect. Therapeutic efficacy in vivo has its limitations due to the hypercalcemia observed with high dose treatment of the parent 1,25-dihydroxycholecalciferol. As a result, a number of analogues have been developed that produce significant anti-tumor effects without hypercalcemia.
Steinmeyer et al in U.S. Pat. No. 5,585,368 discloses 1xcex1-25-dihydroxy-20-disubstituted vitamin D3 analogs for the treatment of hyperproliferative disorders of the skin, malignant tumors such as leukemia, colon and breast cancers, autoimmune diseases such as diabetes and for the treatment of sebaceous gland diseases. Danielsson, C. et al in J. Cell Biochem., 63, No. 2, 199-206 (1996) disclose 20-methyl analogues of 1,25-dihydroxy vitamin D3, including 1xcex1-25-dihydroxy-20-methyl-23(E)-ene-cholecalciferol for the treatment of hyperproliferative disorders. This invention provides novel vitamin D3 derivatives for the treatment of hyperproliferative disorders of the skin, malignant tumors such as leukemia, colon and breast cancers, autoimmune diseases such as diabetes and for the treatment of sebaceous gland diseases which have more favorable therapeutic ratios or margins.
c. Hyperparathyroidism
Secondary hyperparathyroidism is routine in patients with chronic renal failure. It is established that the reduction of renal 1,25(OH)2 vitamin D3 (calcitriol) synthesis is one of the principal mechanisms leading to the secondary hyperparathyroidism in these patients and it has been shown that calcitriol possesses direct suppressive action on PTH synthesis. Therefore, administration of calcitriol has been recommended for the treatment of secondary hyperparathyroidism in these patients. However, as described above, calcitriol has potent hypercalcemic effects giving it a narrow therapeutic window which limits its usage, especially at high doses. It would therefore be desirable to have an alternative means of treating hyperparathyroidism and repleting circulating vitamin D3 activity without incurring these undesirable hypercalcemic effects.
This invention provides novel vitamin D3 derivatives which have more favorable therapeutic windows.
One aspect of the invention concerns Vitamin D3 analogs of the Formula (I): 
wherein:
X is hydrogen or xe2x95x90CH2;
R1 and R2 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl, or R1 and R2 together form xe2x95x90CH2;
R3 and R4 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R3 and R4 together with C25 form a (C3-C9)cycloalkyl or (C3-C9)cyclofluoroalkyl;
A is a single or a double bond; and
B is a single, double or triple bond;
and prodrugs thereof, provided that:
(i) when R1 and R2 are (C1-C4)alkyl or R1 and R2 together with C20 form a cyclopropyl group or xe2x95x90CH2, R3 and R4 are (C1-C4)alkyl, trifluoromethyl or R3 and R4 together with C25 form (C3-C6)cycloalkyl and A is a single bond, then B is not a trans double bond;
(ii) when B is a single bond, then R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl group; and
(iii) when R1 and R2 are (C1-C4)alkyl, R3 and R4 are (C1-C4)alkyl, Xxe2x95x90CH2 and A is a single bond, then B is not a double bond.
A second aspect of this invention relates to a method for treating osteoporosis or secondary hyperparathyroidism via administration of a compound of Formula (I), wherein:
X is hydrogen or xe2x95x90CH2;
R1 and R2 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl, or R1 and R2 together form xe2x95x90CH2;
R3 and R4 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R3 and R4 together with C25 form a (C3-C9)cycloalkyl or (C3-C9)cyclofluoroalkyl;
A is a single or a double bond; and
B is a single, double or triple bond;
and prodrugs thereof, in an amount therapeutically effective to restore bone density to an asymptomatic level, without inducing hypercalciuria, hypercalcemia, or nephrotoxicity.
A third aspect of this invention relates to a method for treating cancer via administration of a compound of Formula (I), wherein:
X is hydrogen or xe2x95x90CH2;
R1 and R2 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl, or R1 and R2 together form xe2x95x90CH2;
R3 and R4 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R3 and R4 together with C25 form a (C3-C9)cycloalkyl or (C3-C9)cyclofluoroalkyl;
A is a single or a double bond; and
B is a single, double or triple bond;
and prodrugs thereof, in an amount therapeutically effective, without inducing hypercalciuria, hypercalcemia, or nephrotoxicity provided that:
(i) when R1 and R2 are (C1-C4)alkyl or R1 and R2 together with C20 form a cyclopropyl group or xe2x95x90CH2, R3 and R4 are (C1-C4)alkyl, trifluoromethyl or R3 and R4 together with C25 form (C3-C6)cycloalkyl and A is a single bond, then B is not a trans double bond;
(ii) when B is a single bond, then R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl group; and
(iii) when R1 and R2 are (C1-C4)alkyl, R3 and R4 are (C1-C4)alkyl, Xxe2x95x90CH2 and A is a single bond, then B is not a double bond.
A fourth aspect of this invention relates to pharmaceutical compositions comprising a pharmaceutically acceptable carrier and a vitamin D3 analog of Formula (I).
The vitamin D3 analogs of the present invention have the following general structure: 
wherein:
X is hydrogen or xe2x95x90CH2;
R1 and R2 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl, or R1 and R2 together form xe2x95x90CH2;
R3 and R4 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R3 and R4 together with C25 form a (C3-C9)cycloalkyl or (C3-C9)cyclofluoroalkyl;
A is a single or a double bond; and
B is a single, double or triple bond;
and prodrugs thereof, provided that:
(i) when R1 and R2 are (C1-C4)alkyl or R1 and R2 together with C20 form a cyclopropyl group or xe2x95x90CH2, R3 and R4 are (C1-C4)alkyl, trifluoromethyl or R3 and R4 together with C25 form (C3-C6)cycloalkyl and A is a single bond, then B is not a trans double bond;
(ii) when B is a single bond, then R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl group; and
(iii) when R1 and R2 are (C1-C4)alkyl, R3 and R4 are (C1-C4)alkyl, Xxe2x95x90CH2 and A is a single bond, then B is not a double bond.
A method for treating osteoporosis or secondary hyperparathyroidism via administration of a compound of Formula (I), wherein:
X is hydrogen or xe2x95x90CH2;
R1 and R2 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl, or R1 and R2 together form xe2x95x90CH2;
R3 and R4 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R3 and R4 together with C25 form a (C3-C9)cycloalkyl or (C3-C9)cyclofluoroalkyl;
A is a single or a double bond; and
B is a single, double or triple bond;
and prodrugs thereof, in an amount therapeutically effective to restore bone density to an asymptomatic level, without inducing hypercalciuria, hypercalcemia, or nephrotoxicity.
A method for treating cancer via administration of a compound of Formula (I), wherein:
X is hydrogen or xe2x95x90CH2;
R1 and R2 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl, or R1 and R2 together form xe2x95x90CH2;
R3 and R4 are, independently of each other, a (C1-C4)alkyl or (C1-C4)fluoroalkyl, or R3 and R4 together with C25 form a (C3-C9)cycloalkyl or (C3-C9)cyclofluoroalkyl;
A is a single or a double bond; and
B is a single, double or triple bond;
and prodrugs thereof, in an amount therapeutically effective, without inducing hypercalciuria, hypercalcernia, or nephrotoxicity, provided that:
(i) when R1 and R2 are (C1-C4)alkyl or R1 and R2 together with C20 form a cyclopropyl group or xe2x95x90CH2, R3 and R4 are (C1-C4)alkyl, trifluoromethyl or R3 and R4 together with C25 form (C3-C6)cycloalkyl and A is a single bond, then B is not a trans double bond;
(ii) when B is a single bond, then R1 and R2 together with C20 form a (C3-C6)cycloalkyl or (C3-C6)cyclofluoroalkyl group; and
(iii) when R1 and R2 are (C1-C4)alkyl, R3 and R4 are (C1-C4)alkyl, Xxe2x95x90CH2 and A is a single bond, then B is not a double bond.
As used herein, the term (C1-C4) alkyl means a fully-saturated hydrocarbon radical having one to four carbon atoms; a (C1-C4) fluoroalkyl is an alkyl radical, as defined above, in which one or more hydrogen atoms attached to the carbon backbone have been substituted with one or more fluorine atoms. A (C3-C6) cycloalkyl is a cyclic saturated hydrocarbon radical having three to six ring carbon atoms; a (C3-C6) cyclofluoroalkyl is a cycloalkyl radical, as defined above, in which one or more hydrogen atoms attached to the carbon backbone have been substituted with one or more fluorine atoms. A (C3-C9) cycloalkyl is a cyclic saturated hydrocarbon radical having three to nine ring carbon atoms; a (C3-C9) cyclofluoroalkyl is a cyclic saturated hydrocarbon radical having three to nine carbon atoms in which one or more hydrogen atoms attached to the carbon backbone have been substituted with one or more fluorine atoms.
Further as used herein, by double bond it is meant an unsaturated linkage between two adjacent carbon atoms in which two pairs of electrons are shared equally, and wherein each carbon atom bears two single-bonded substituents in either a cis (Z) or a trans (E) configuration about the double bond.
xe2x80x9cPro-drugsxe2x80x9d means any compound which releases an active parent drug according to Formula (I) in vivo when such prodrug is administered to a mammalian subject. Prodrugs of a compound of Formula (I) are prepared by modifying functional groups present in the compound of Formula (I) in such a way that the modifications may be cleaved in vivo to release the parent compound. Prodrugs include compounds of Formula (I) wherein a hydroxy group in compound (I) is bonded to any group that may be cleaved i vivo to regenerate the free hydroxyl group. Examples of prodrugs include, but are not limited to esters (e.g., acetate, formate, and benzoate derivatives), carbamates (e.g., N,N-dimethylaminocarbonyl) and ethers of hydroxy functional groups in compounds of Formula (I), and the like. Such compounds are routinely made by one of skill in the art by acylating or etherifying the hydroxy group in the parent molecule.
A xe2x80x9ctherapeutically effective amountxe2x80x9d means the amount of a compound that, when administered to a mammal for treating or preventing a disease, is sufficient to effect such treatment or prevention for the disease. The xe2x80x9ctherapeutically effective amountxe2x80x9d will vary depending on the compound, the disease and its severity and the age, weight, etc., of the mammal to be treated.
The compounds of the present invention may be generically described as 1xcex1,25-dihydroxy-20,20-dialkyl and 1xcex1,25-dihydroxy-20,20-dialkyl-19-nor analogs of vitamin D3.
The compounds of the invention are named using the numbering system shown in FIG. (1) below. 
For example, a compound of the invention where X is xe2x95x90CH2, R1 and R2 together form a cyclopropyl group, A is a single bond and B is a triple bond is named as 1xcex1-25-dihydroxy-23-yne-20,21,28-cyclopropyl-cholecalciferol.
The following Table I provides some representative examples of compounds of the present invention:
and are named as:
1. 1,25-dihydroxy-23-yne-20,21,28-cyclopropyl-cholecalciferol.
2. 1,25-dihydroxy-23-yne-20,21,28-cyclopropyl-19-nor-cholecalciferol.
3. 1,25-dihydroxy-23-yne-26,27-hexafluoro-20,21,28-cyclopropyl-cholecalciferol.
4. 1,25-dihydroxy-23-yne-26,27-hexafluoro-20,21,28-cyclopropyl-19-norcholecalciferol.
5. 1,25-dihydroxy-23-(Z)-ene-26,27-hexafluoro-20,21,28-cyclopropyl-cholecalciferol.
6. 1,25-dihydroxy-23-(Z)-ene-26,27-hexafluoro-20,21,28-cyclopropyl-19-norcholecalciferol.
While the broadest definition of this invention is set forth in the Summary of the Invention, certain compounds of Formula (I) are preferred.
A preferred group of compounds are those wherein:
A is a single or a double bond, preferably a single bond; and
B is a triple bond.
Another preferred group of compounds are those wherein:
A is a double bond; and
B is a double bond.
Yet another preferred group of compounds are those wherein:
A is a single or a double bond, preferably a single bond; and
B is a cis double bond.
Within these preferred groups of compounds, more preferred groups are those wherein:
R1 and R2 together with C20 form a (C3-C6)cycloalkyl, preferably a cyclopropyl; and
R3 and R4 are, independently of each other, a (C1-C4)alkyl or a (C1-C4)fluoroalkyl, preferably methyl, ethyl, trifluoromethyl, 1,1-difluoroethyl or 2,2,2-trifluoroethyl, more preferably methyl or trifluoromethyl.
Analogs of this invention may generally be prepared by reaction and combination of fragments of Vitamin D3 molecules (see e.g., Shiuey et al., J. Org. Chem, 55:243 (1990); Wovkulich, P. M. et al., Tetrahedron, 40, 2283 (1984); Baggiolini E. B. et al J. Org. Chem., 51, 3098-3108, (1986) and Steinmeyer et al., U.S. Pat. No. 5,585,368.
The starting materials and reagents used in preparing these compounds are either available from commercial suppliers such as Aldrich Chemical Co., (Milwaukee, Wis.), or Sigma (St. Louis, Mo.) or they can be prepared by methods known to those skilled in the art following procedures set forth in references such as Fieser and Fieser""s Reagents for Organic Synthesis, Vol. 1-15 (John Wiley and Sons, 1991); March""s Advanced Organic Chemistry, (John Wiley and Sons 4th Edition) and Larock""s Comprehensive Organic Transformations (VCH Publishers Inc., 1989).
The starting materials and the intermediates of the reaction may be isolated and purified if desired using conventional techniques, including but not limited to filtration, distillation, crystallization, chromatography and the like. Such materials may be characterized using conventional means, including physical constants and spectral data.
The preparation of compounds of Formula (I) and the intermediates used in their preparation is illustrated by the reaction schemes below.
In general, a compound of Formula (I) is prepared by coupling a 4H-inden-4-one derivative of Formula (II) where R1, R2, R3, R4, A and B are as described in the Summary of the Invention and R5 is hydrogen or a hydroxy protecting group (e.g., trialkylsilyl, preferably trimethylsilyl) with a diphenylphosphine oxide derivative of a compound of Formula (III) where X is hydrogen or xe2x95x90CH2, as shown in Scheme I below. 
The coupling reaction is carried out in the presence of a strong base such as an alkyllithium like n-butyllithium in a mixture of hexane and tetrahydrofuran at xe2x88x9278xc2x0 C. to give a trisily derivative of compound of Formula (I). Removal of the sily protecting groups with tetrabutylammnonium fluoride in a suitable polar organic solvent such as tetrahydrofuran provides a compound of Formula (I).
It should be noted that although the shown intermediates have hydroxy groups typically protected as silylethers, the scope of the invention includes the use of alternative hydroxyl protecting groups known in the art as described in T. W. Greene, xe2x80x9cProtective Groups in Organic Synthesis,xe2x80x9d Wiley, New York (1991) and J. F. McOmie, xe2x80x9cProtective Groups in Organic Chemistry,xe2x80x9d Plenum Press, London (1973), together with alternative methods for deprotection.
Synthesis of compounds of Formula (III) are known and conventional in this art. See, for example, U.S. Pat. No., 5,585,368 to Steinmeyer et al., U.S. Pat. No. 5,384,314 to Doran et al., U.S. Pat. No. 5,428,029 to Doran et al., U.S. Pat. No. 5,451,574 to Baggiolini et al.; pending U.S. patent application Ser. No. 60/018,219; Shiuey et al., J. Org. Chem., 55:243-247 (1990), Kiegel, J. et al. and Tetr. Lett., 32:6057-6060 (1991), Perlman, K. L., et al., Tetr. Lett., 32:7663-7666 (1991).
Synthesis of compounds of Formula (II) is described in Scheme II below.
Detailed descriptions of the synthesis of compounds of Formula (I) where R1 and R2 together form a cyclopropyl ring, X is xe2x95x90CH2 or H2, A is a single bond, B is a triple bond and R3 and R4 are either methyl or trifluoromethyl are described in Examples 2, 3, 5 and 6.
Detailed descriptions of the synthesis of compounds of Formula (I) where R1 and R2 together form a cyclopropyl ring, X is xe2x95x90CH2 or H2, A is a single bond, B is a cis double bond and R3 and R4 are trifluoromethyl are described in Examples 8 and 9.
The 4H-inden-4-one derivatives of Formula (II) are prepared as shown in Scheme II below. 
As shown above, preparation of a compound of Formula (II) involves preparation of a common intermediate, 1-[(5-hydroxy)-3-alkynyl]-inden-4-ol derivative (VII), which is then converted to a compound of Formula (II) where B is either a double or a triple bond by following method (a) or method (b) respectively.
Compound (VII) is prepared by condensation of lithium acetylide derived from a 1-(3-alkynyl)-4-tert-butyldimethylsilyloxy-7a-methyl-indene derivative (IV) with a ketone of Formula (V) where R3 and R4 are as defined in the Summary of the Invention to give a 1-[(5-hydroxy)-3-alkynyl]-4-tert-butyldimethysilyloxy-7a-methyl-indene derivative (VI). The condensation reaction is carried out in the presence of a strong base such as n-butyllithium in an aprotic organic solvent such as tetrahydrofuran and at low temperatures ranging between xe2x88x9250 to xe2x88x92100xc2x0 C. Removal of the silyl group with tetrabutylammonium fluoride in an suitable organic solvent such as tetrahydrofuran gives the 1-[(5-hydroxy)-3-alkynyl]-inden-4-ol derivative (VII).
A detailed description of the synthesis of compounds of Formula (IV) where R1 and R2 together form a cyclopropyl ring and A is a single bond is given in Example 1. Synthesis of other compounds of Formula (IV) and alternative methods for preparing compounds of Formula (VII) have been described in copending U.S. application Ser. No. 08/857,569, published as EP 0 808,832 A2, whose disclosure is hereby incorporated by reference.
A compound of Formula (II) where B is a triple bond and R5 is hydrogen is prepared, as shown in method (a), by oxidation of the hydroxy group at the 4-position in compound (VII) to the keto group with a suitable oxidizing agent such as pyridinium dichromate at room temperature. The oxidation reaction is carried out in a chlorinated hydrocarbon solvent such as methylene chloride, chloroform and the like. A compound of Formula (II) where R5 is hydrogen is converted to the corresponding compound of Formula (II) where R5 is trialkylsilyl, preferably trimethylsilyl, by reacting it with a suitable silylating agent such as 1-trimethylsilylimidazole in a non-alcoholic organic solvent such as tetrahydrofuran, methylene chloride, preferably methylene chloride, and the like.
Synthesis of compounds of Formula (II) where A is a single bond, B is a triple bond, R1 and R2 together form a cyclopropyl ring, R1 is trimethylsilyl or hydrogen and R3 and R4 are methyl or trifluoromethyl are described in Examples 1 and 4.
Alternatively, a compound of Formula (II) where B is a double bond is prepared, as shown in method (b), by partial reduction of the triple bond in compound (VII) with a suitable reducing agent to give a 3-alkene-4H-inden-4-ol of Formula (VIII). The choice of the reducing agent depends on the configuration about the double bond. If the E configuration is desired, then the reduction is carried out with lithium aluminum hydride in the presence of an alkali metal alkoxide, such as sodium methoxide, and in an aprotic organic solvent like ether or more preferably tetrahydrofuran. If the Z configuration is desired, then the reduction is carried out with Lindlar""s catalyst. Compound (VIII) is then converted to a compound of Formula (II) where B is a double bond and R5 is hydrogen or a silyl group by carrying out the oxidation and silylation steps as described above. Synthesis of a compound of Formula (II) where A is a single bond, B is a cis double bond, R1 and R2 together form a cyclopropyl ring, R5 is trimethylsilyl and R3 and R4 are trifluoromethyl is described in Example 7.
A reaction scheme showing the preparation of a compound of Formula (I) where A is a single bond, B is a single bond, R1 and R2 form a cyclopropyl ring and X is xe2x95x90CH2 is shown below in Scheme III and is described further in Example 10. 
The starting material is reduced, preferably by catalytic hydrogenation, to give the completely saturated side chain derivative which is then oxidized to give the corresponding ketone. Condensation with a diphenylphosphine oxide as previously described in Scheme I followed by removal of the silyl protecting groups gives the desired compound. One of skill in the art will recognize that similar procedures may be used to form other compounds of the invention where R1-R4 and X may vary as described in the Summary of the Invention.
The compounds of this invention are useful for the prevention and treatment of a variety of mammalian conditions manifested by loss of bone mass. In particular, the compounds of this invention are anabolic agents and are indicated for the prophylaxis and therapeutic treatment of osteoporosis and osteopenia in mammals without inducing hypercalciuria, hypercalcemia, or nephrotoxicity. As used herein, xe2x80x9chypercalciuriaxe2x80x9d is excessive calcium in the urine, in humans corresponding to an excretion of greater than about 4 mg/kg/day. This often results in nephrolithiasis (renal calculi). xe2x80x9cHypercalcemiaxe2x80x9d is an excessive concentration of calcium in the serum; in humans (and rats) this corresponds to greater than about 10.5 mg/dl. xe2x80x9cIntolerable hypercalcemiaxe2x80x9d, usually occurring at serum calcium concentrations greater than about 12 mg/dl, is associated with emotional lability, confusion, delirium, psychosis, stupor, and coma.
The compounds of this invention are expected to be useful in the treatment of Type I (postmenopausal), Type II (senile), and Type III (iatrogenic) osteoporosis, including that associated with immunosuppressive drugs used in organ transplantation, as well in the treatment of osteodystrophy due to renal dialysis and secondary hyperparathyroidism.
Compounds of this invention are also useful in treating diseases caused by elevated levels of parathyroid hormone. In one aspect, compounds of the invention are used in treating secondary hyperparathyroidism associated with renal failure and in particular with reversing or reducing the bone loss associated with renal insufficiency. Other aspects include the treatment of renal osteodystrophy associated with late stage secondary hyperparathyroidism. Other aspects include the treatment of primary hyperparathyroidism.
Compounds of Formula (I) are also useful in treating neoplastic diseases such as leukemia, colon cancer, breast cancer and prostate cancer.
Compounds of Formula (I) are also useful in treating immunosuppressive and autoimmune diseases. Such diseases include, but are not limited to, multiple sclerosis, systemic lupus erythematosus, diabetes, thyroiditis and allograft rejection. In particular, compounds of Formula (I) are useful to treat diseases via modulation of the activity of the vitamin D3 receptor (VDR). The utility of these compounds is demonstrated in vivo using murine models for these diseases as is well known in the art. See, e.g., Lemire et al., Autoimmunity, 12:143-148 (1992); Lemireet. al., J. Clin. Invest., 87:1103-1107 (1991), Lemire et al., Endocrinology, 135:2818 (1994), and Lemire et al., J. Cellular Biochem., 49:26-31 (1992).
The bone anabolic activity of the compounds of the invention was demonstrated in vivo in the ovariectomized rat model as described in detail in Example 10. The anti-cell proliferation activity of the compounds of the invention was demonstrated in vitro as described in detail in Examples 11 and 12. The parathyroid hormone suppressive activity of the compounds of the invention was demonstrated in vivo as described in detail in Example 13.
In general, the compound of this invention may be administered in amounts between about 0.0002 and 5 xcexcg per day, preferably from about 0.001 to about 2 xcexcg per day, most preferably from about 0.002 to about 1 xcexcg per day. For a 50 xcexcg human subject, the daily dose of active ingredient may be from about 0.01 to about 250 xcexcg, preferably from about 0.05 to about 100 xcexcg, most preferably from about 0.1 to about 50 xcexcg per day. In other mammals, such as horses, dogs, and cattle, other doses may be required. This dosage may be delivered in a conventional pharmaceutical composition by a single administration, by multiple applications, or via controlled release, as needed to achieve the most effective results, preferably once or twice daily by mouth. In certain situations, alternate day dosing may prove adequate to achieve the desired therapeutic response.
The selection of the exact dose and composition and the most appropriate delivery regimen will be influenced by, inter alia, the pharmacological properties of the formulation, the nature and severity of the condition being treated, and the physical condition and mental acuity of the recipient. In the treatment of corticosteroid induced osteopenia, it is expected that the requisite dose will be greater for higher doses of corticosteroids.
Representative delivery regimens include oral, parenteral (including subcutaneous, intramuscular and intravenous), rectal, buccal (including sublingual), pulmonary, transdermal, and intranasal, most preferably oral.
A further aspect of the present invention relates to pharmaceutical compositions comprising as an active ingredient a compound of the present invention, in admixture with a pharmaceutically acceptable, non-toxic carrier. As mentioned above, such compositions may be prepared for parenteral (subcutaneous, intramuscular or intravenous) administration, particularly in the form of liquid solutions or suspensions; for oral or buccal administration, particularly in the form of tablets or capsules; for pulmonary or intranasal administration, particularly in the form of powders, nasal drops or aerosols; and for rectal or transdermal administration.
The compositions may conveniently be administered in unit dosage form and may be prepared by any of the methods well-known in the pharmaceutical art, for example as described in Remington""s Pharmaceutical Sciences, 17th ed., Mack Publishing Company, Easton, Pa., (1985). Formulations for parenteral administration may contain as excipients sterile water or saline, alkylene glycols such as propylene glycol, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, hydrogenated naphthalenes and the like. Formulations for nasal administration may be solid and may contain excipients, for example, lactose or dextran, or may be aqueous or oily solutions for use in the form of nasal drops or metered spray. For buccal administration typical excipients include sugars, calcium stearate, magnesium stearate, pregelatinated starch, and the like.
Orally administrable compositions may comprise one or more physiologically compatible carriers and/or excipients and may be in solid or liquid form, including, for example, tablets, coated tablets, capsules, lozenges, aqueous or oily suspensions, solutions, emulsions, elixirs, and powders suitable for reconstitution with water or another suitable liquid vehicle before use. Tablets and capsules may be prepared with binding agents, for example, syrup, acacia, gelatin, sorbitol, tragacanth, or poly-vinylpyrollidone; fillers, such as lactose, sucrose, corn starch, calcium phosphate, sorbitol, or glycine; lubricants, such as magnesium stearate, talc, polyethylene glycol, or silica; and surfactants, such as sodium lauryl sulfate. Liquid compositions may contain conventional additives such as suspending agents, for example sorbitol syrup, methyl cellulose, sugar syrup, gelatin, carboxymethylcellulose, or edible fats; emulsifying agents such as lecithin, or acacia; vegetable oils such as almond oil, coconut oil, cod liver oil, or peanut oil; preservatives such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Liquid compositions may be encapsulated in, for example, gelatin to provide a unit dosage form.
Preferred solid oral dosage forms include tablets, two-piece hard shell capsules and soft elastic gelatin (SEG) capsules. SEG capsules are of particular interest because they provide distinct advantages over the other two forms (see Seager, H., xe2x80x9cSoft gelatin capsules: a solution to many tableting problemsxe2x80x9d; Pharmaceutical Technology, 9, (1985). Some of the advantages of using SEG capsules are: a) dose-content uniformity is optimized in SEG capsules because the drug is dissolved or dispersed in a liquid that can be dosed into the capsules accurately, b) drugs formulated as SEG capsules show good bioavailability because the drug is dissolved, solubilized or dispersed in an aqueous-miscible or oily liquid and therefore when released in the body produce drug dispersions of high surface area and c) degradation of drugs that are sensitive to oxidation during long-term storage is prevented because the dry shell of soft gelatin provides a barrier against the diffusion of oxygen.
The dry shell formulation typically comprises of about 40% to 60% concentration of gelatin, about a 20% to 30% concentration of plasticizer (such as glycerin, sorbitol or propylene glycol) and about a 30 to 40% concentration of water. Other materials such as preservatives, dyes, opacifiers and flavours also may be present. The liquid fill material comprises a solid drug that has been dissolved, solubilized or dispersed (with suspending agents such as beeswax, hydrogenated castor oil or polyethylene glycol 4000) or a liquid drug in vehicles or combinations of vehicles such as mineral oil, vegetable oils, triglycerides, glycols, polyols and surface-active agents.